Mechanisms of Chronic Rhinosinusitis

Photomicrographs of CRS specimens stained with Hematoxylin & Eosin (left) or stained for eosinophil major basic protein (MBP) by immunofluorescence (right). On the left the figure demonstrates eosinophilic inflammation in tissue (lower part of image), eosinophil clusters (black arrows) in mucus, subepithelial basement membrane thickening and damaged epithelium (yellow arrows) (original magnification x 160). On the right the serial section shows that MBP in subepithelial tissue is contained within the cells or in intact granules (punctate staining) outside the cells. In mucus, diffuse MBP staining is in eosinophil clusters (white arrows) and outside of clusters (anti MBP, original magnification x 160).

This immunofluorescence photomicrograph uses the dye, fluorescein, attached to an antibody specific for a protein in eosinophil granules, called eosinophil major basic protein, to detect and locate eosinophils. It shows how the eosinophils (shown by the bright yellow/green colored areas) cluster around and along the hyphal growth (shown as faintly colored threads) of the fungus known as Alternaria. It also shows that the major basic protein has been released from eosinophils and has been localized on the surfaces of these fungal hyphae. These human eosinophils were incubated for several hours in a culture with live fungal hyphae before being fixed in formalin and stained with the specific antibody to eosinophil major basic protein. (Original Magnification X400)

This vividly colored quartet of images is an esthetic tribute to the work of certain graphic artists, and the colored enhancements were provided to the ADRL by the Mayo Rochester Section of Photography. Each identical image shows a view from a scanning electron microscope that provides a 3-dimensional perspective at very high magnification. The large sphere in the upper right is an eosinophil and the tube-like shape on the left is a part of a hyphal growth of the fungus Alternaria. There appears to be a substance coming from the eosinophil that is partially covering the fungus. One hypothesis under current testing is that eosinophils are part of an immune system attack response to certain microbes, including the fungus Alternaria.

We are studying the mechanisms that chronically activate immune cells in patients with allergic disorders, such as asthma and chronic rhinosinusitis (CRS). This involves the responses of immune cells, such as lymphocytes and NK cells, to common environmental antigens in patients. We tested the blood cells involved in immunity from 18 patients with chronic rhinosinusitis and found that their cells showed exaggerated responses to the common airborne fungi, Alternaria alternata. Blood cells involved in immunity from 15 normal individuals did not respond. This anomalous response to ubiquitous environmental fungi might explain the persistent airway inflammation in chronic rhinosinusitis patients. We are also studying the pathologic mechanisms of eosinophils in human diseases in vivo. In particular, how does eosinophilia (extraordinary increases in eosinophil number) occur in patients, how do eosinophils infiltrate into the tissues, and how do eosinophils become activated in local inflammatory sites. In studying the role of fungal organisms in the development of airway inflammation with many eosinophils, we used an anti-fungal medication. This randomized, placebo-controlled, double-blind pilot treatment in chronic sinusitis patients used irrigation of the nose (twice a day) with an anti-fungal medication versus patients treated with placebo for six months. The patients treated with medication had less swelling in their nasal passages and reduced levels of a protein associated with eosinophils in their mucus. Also, biopsy specimens obtained during surgical treatment from chronic rhinosinusitis patients show clusters of eosinophils and eosinophil granule proteins in the mucus.

Eosinophils were not found in healthy normal control tissues and mucus. In the laboratory, eosinophils from healthy people do become activated and degranulate, when they are exposed to Alternaria or to one other fungus, Penicillium, but not to 5 other fungi. Preliminary analyses of the glycoproteins and other components in Alternaria and the biochemical response mechanisms shown by the eosinophils are also described. These results provide many new avenues to better understand the immunological responses by human cells and tissues to a common environmental fungus and to develop novel treatment strategies for patients.

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